If you are in my fall 2021 class, this is the file you download

1. Ch. 9 Review
This is gunna be ALKYNES of fun!
Daniel Eisenstein and

2. Alkynes
• Undergo similar reactions as alkenes
• Sp hybridized
• linear geometry= 180 bond angle
• Have general formula CnH2n-2

3. Alkynes (cont.)
• Terminal alkyne: alkyne at end
• Internal alkyne: internal
• Second pi bond is weaker than first
• No special physical properties

4. Nomenclature
• Change –ane to –yne
• Has same priority as alkene
• 2 alkynes? –diyne
• 3 alkynes? -triyne

5. Practice

6. Reactivity
• Addition across pi bond
• If it is terminal, C-H bond is acidic
• Therefore can be deprotonated by strong base (like NH2-)

8. Hydrohalogenation
• hydrohalogenation forms a geminal dihalide

9. Halogenation
• Halogenation forms a tetrahalide product

10. Acid-Catalyzed Hydration
• Uses H2O, H2SO4 as well as an HgSO4 catalyst
• Initial product is enol
• Enol tautomerizes to ketone
• Mechanism

11. Hydration mech (part 1)
Part 2 of the mechanism is called a tautomerization

12. Tautomerization

13. Tautomers
• Enol  keto
• Mechanism
• Constitutional isomers

14. Practice

15. Hydroboration oxidation
• Internal alkyne yields ketone
• Terminal alkyne yields aldehyde
• If terminal, we use R2BH
• If internal, we use BH3

16. Practice

17. Acetylide Anions
• -:C≡C-R
• We take a terminal alkyne
• Use strong base
• Strong base include NaH and NaNH2
• Mechansim

18. Acetylide anion formation

19. Reactions of acetylide anions
• Sn2 if primary
• If LG is secondary or tertiary we go E2
• Acetylide is a strong B: and Nu:

20. Practice

21. Preparing for Synthesis
• I want you guys to know Ch. 7,8,9,10
• Know ALL reagents and ALL products
• This is one of the hardest concepts in Orgo 1

22. My Method For Synthesis
• 1st step: retrosynthetic analysis
• Identify functional groups in your product and reactant
• Ask: what can this reactant do? (can I add to it? Eliminate? Substitute
maybe?...etc.)
• Ask: how can this product be formed? Addition? Elimination, substitution?
• Use these questions to guide where you go with the structures of the
intermediates

23. My methods (cont.)
• Step 2:
• If your retrosynthetic analysis is good
• Find reagents that make your reaction work out
• *Keep regioselectivity and stereoselectivity in mind

24. Retrosynthetic analysis
• You will be given a product and a reactant
• You need to be able to identify every reactive intermediate
• Use an “open” arrow going from product to intermediate
• Then from intermediate(s) to reactant
• We are working backwards

25. Synthesis
• If you have your retrosynthetic analysis right, this is easy
• Start with the reactant
• Find the reagents needed to convert the reactant to the
intermediate
• Repeat until all reagents are identified

26. Practice